That is quite interesting. The livedocs page associates uniqueidentifier
with both varchar and idstamp.
The funny thing is, they don't seem to be much different. If you run a
trace on your database to capture the statement being prepared, your
parameter is declared as varchar(8000) whether or not you use
cf_sql_varchar or cf_sql_idstamp.
At least, that's what I just saw using CF8 and SQL Server 2000.
~Brad